Endocytic internalization routes required for delta/notch signaling

Area of Science:

• Cell biology
• Molecular and Developmental Biology

Background:

• Receptor internalization regulates cell signaling.
• Distinct endocytic routes mediate receptor trafficking, but their roles in signaling are unclear.
• The Delta-Notch pathway is crucial for development and cell-cell communication.

Purpose of the Study:

• To elucidate the specific endocytic pathways required for Delta-Notch signaling and receptor regulation.
• To differentiate between endocytic routes for receptor degradation versus signaling activation.
• To investigate the mechanism of Delta ligand activation.

Main Methods:

• Utilized null mutations in Drosophila dynamin, clathrin, and AP-2 adaptor subunits.
• Analyzed internalization requirements for the Delta ligand and Notch receptor.
• Investigated endosomal entry and Rab11 effector activity in Delta signaling.

Main Results:

• Bulk Notch receptor internalization is AP-2-dependent.
• Notch signaling requires AP-2-independent, clathrin-dependent endocytosis.
• Delta signaling in germline cells can occur via clathrin-independent endocytosis, independent of Rab11 activity.
• Delta signaling supports a
• pulling force
• model over a recycling pathway.

Conclusions:

• Endocytic route choice dictates Notch receptor fate (degradation vs. signaling).
• Delta signaling activation in germline cells does not necessitate passage through canonical recycling pathways.
• Findings support a model where dynamin-dependent endocytosis generates a pulling force for Delta-mediated Notch activation.